Quadratics and Cubics, SMB-036 Using the quadratic formula, find `a` given `5a^2+7a-1 = 0.` (3 marks) Show Answers Only `(-7 +- sqrt(69) )/10` Show Worked Solution `5a^2+7a-1 = 0` `text(Using)\ a = (-b +- sqrt( b^2-4ac) )/(2a)` `a` `= (-7 +- sqrt{(7)^2-4 xx 5 xx(-1) })/ (2 xx 5)` `= (-7 +- sqrt(49+20) )/10` `= (-7 +- sqrt(69) )/10`